The student should familiarise himself with the “seed" of Phleum pratense, as a type, and an important grass easily obtained pure, but sometimes with minute round seeds of weeds intermixed.
Phleum pratense, L. (Fig. [45]).
Palea 2·3 mm. long, five-ribbed, with a short point, delicate but hard, smooth, with a silvery lustre. Inner pale two-nerved. Closely investing the yellow-brown
caryopsis, which easily falls out and is ovoid-acute, about 2 mm. long by 1 broad, and finely punctate.
The much rarer P. arenarium and the very rare P. Bœhmeri and P. asperum also come here.
Phleum is not easily confounded with any other of our grasses, and Briza and Glyceria are almost the only other common grasses of about the same size of which the caryopsis often falls free from the palea ("naked fruits"). Glyceria is longer and corn-shaped, and Briza usually larger. Anthoxanthum and Phalaris are easily distinguished. Agrostis is smaller and “corn-shaped." Certain species of Panicum present resemblances, but the enveloping paleæ, &c. are very different. Melica also occurs as “naked fruits,” but is rarely seen, and its colour and brilliant lustre distinguish it.
B. Glumes not cuspidate. “Fruit" not yellow.
(a) “Fruit" white, owing to the closely investing palea.
Milium effusum.
A common grass, but not often met with in “seed" grasses. It is eagerly eaten by birds.